Elastomers have the property that the service life of the material is very limited, in particular in the case of the permanent presence or occurrence of tensile stresses. In the design and production of components which comprise elastomers for damping purposes, great care is therefore taken to ensure that tensile stresses cannot occur.
For this reason, elastomer components, e.g. elastomer bushes for wind turbines, are, in accordance with the prior art, pre-stressed after vulcanization of the rubber material. This is generally carried out by calibration.
In the simplest case, an elastomer bush consists of an outer and inner shell, generally made from metal, usually with a round or elliptical shape, where the two shells are connected to one another by an elastomer layer of various thickness. The elastomer bush forms a type of collar, which is placed with its inner shell around the article to be damped (e.g. a shaft or axle of a machine or device to be damped). During calibration, either the outer shell is forced through a tube of relatively small diameter and plastically deformed in the process. This causes the diameter of the outer shell to become smaller, so that pre-stressing of the elastomer located between the outer and inner shell takes place. Conversely, a pre-stress can be generated by forcing a bolt of larger diameter than the inner shell through the latter, which results in expansion of the inner shell towards the outside and thus compression of the elastomer layer between the outer and inner shell.
These two processes can be carried out individually or also together. If the elastomer layer is compressed by the calibration, it is thus pre-stressed in the pressure direction. In the case of radial deformation of the outer shell towards the inner shell, the operation is carried out in this pressure range, meaning that tensile stresses do not occur in the elastomer layer and the service life of the components is assured.
The situation is similar with other elastomer elements, such as layer springs or other bearings or damping means, in which a fairly large elastomer layer has to be compressed to a not inconsiderable extent and thus pre-stressed.
However, the known prior-art process described above can only be achieved at acceptable cost with bushes and bearings having relatively small dimensions (diameter less than 30 cm). The forces that have to be applied in order to pre-stress, or calibrate, relatively large bushes (diameter greater than 30 cm, preferably greater than 100 cm) are on the one hand too great, and on the other hand the terminal or limiting elements or plates would in these cases have to be dimensioned corresponding to their thickness and manufactured from very sturdy material in order that they do not bend up again or deform due to the large internal pressure of the elastomer which has arisen owing to the calibration carried out. Similar problems can be expected in arrangements which are intended to comprise particular materials or have particular shapes and thus cannot be calibrated or can only be calibrated to a limited extent by the known prior-art methods.